Most king crab you buy in a grocery store is pre-cooked and frozen; you just thaw it and heat it, which takes only a few minutes, or serve it cold. Thaw crab overnight in the refrigerator or, if you are in a hurry, run it under cold running water for a few minutes.
Cooking Pre-cooked, Frozen Crab
Since most crab is pre-cooked, the cooking time using any method is no more than 10 minutes.
One of the most common methods of heating pre-cooked king crab is in a colander or steamer basket over a pot of boiling water. Cover it and let it steam. This will take only six to 10 minutes, depending on the size of the crab. You do not want to overcook the crab, just heat it through.
If you don't have a steamer basket or pasta pot, you can boil the crab. Boiling requires only a pot big enough to hold the thawed crab and a few cups of boiling water. Bring water in a pot to a boil. Add salt or seasoning, such as lemon juice, at this point. Drop in the defrosted king crab legs and let them simmer for five to seven minutes, or until they are warm all the way through. Rinse and serve.
If you are preparing large quantities of crab, baking may be the best option. Since you aren't trying to fit the crab legs into a steamer basket or pot of boiling water, you are limited only by the number of baking sheets that will fit in your oven. Crack the thawed leg pieces with a nut cracker, crab cracker or hammer. Place them on a baking sheet and brush them with vegetable oil or melted butter. Bake tat 350 for eight to nine minutes, or until heated through.
Cooking Fresh Crab Legs
For most people, fresh crab legs aren't an option. King crab legs are available fresh only near where they are caught, usually in Alaska and Canada.
If you do have access to fresh king crab legs, cook them the day you buy them. Keep them very cold, on ice if necessary, between the store and your kitchen. Refrigerate them until you cook them.
You can boil or steam fresh king crab legs the same way as frozen ones. Fresh crab legs usually require boiling for 10 minutes or more, depending on their size, and steaming also takes a little longer for fresh crab legs. They are done when they should turn bright red. Unless you live near a crab fishery, you probably will not need to know how to cook fresh crab.